$$ \begin{aligned}\frac{x^2+10x+21}{x^2-6x-27}& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}\frac{x+7}{x-9}\end{aligned} $$ | |
① | Factor both the denominator and the numerator, then cancel the common factor. $\color{blue}{x+3}$. $$ \begin{aligned} \frac{x^2+10x+21}{x^2-6x-27} & =\frac{ \left( x+7 \right) \cdot \color{blue}{ \left( x+3 \right) }}{ \left( x-9 \right) \cdot \color{blue}{ \left( x+3 \right) }} = \\[1ex] &= \frac{x+7}{x-9} \end{aligned} $$ |